In many environments, especially industrial environments, modifying the temperature of various items, i.e., heating or cooling them, is frequently desirable. For example, modular plastic conveyor belts are typically formed by linking many elongate plastic modules, and these modules often need to be cut to size for various applications, as disclosed in U. S. Pat. No. 5,072,640. When the plastic modules are heated, they are easier to cut. In particular, heating the plastic modules allows them to be cut quickly without shattering and with little damage to the cutting blade.
Large, walk-in chambers are sometimes used for heating or cooling. These chambers can house many containers, such as cardboard boxes filled with the items and, therefore, can heat or cool a large number of items simultaneously. However, the local velocity of the air in the large space within a walk-in chamber is very low; so it can take a long time to heat or cool the items, especially when they are enclosed in a container. In addition, the items must be transported from a storage site or a work station to the walk-in chamber and then returned to the storage site or work station after they are heated or cooled. Not only is this time consuming but during transportation, heated items may become cool or cooled items may become warm, thus negating the heating or cooling effects of the walk-in chamber. Further, for a single container or for a small number of items, a large walk-in chamber is both uneconomical and inefficient.
Smaller ovens or coolers are sometimes used to modify the temperature of the items. However, these devices typically have small doors to minimize heat transfer into or out of the device, and it is difficult to fit an entire container through the door and in the device. Therefore, the items are frequently unloaded from the container, loaded into the oven or cooler, heated or cooled, unloaded from the oven or cooler, and repacked in the container. Again, this is time consuming and risks negating the heating or cooling effected by the oven or cooler. In addition, the local velocity of the air in a typical oven or cooler can be fairly low; so again it takes a long time to heat or cool the items.